CN103744092A - High-precision time service card applied to task navigation - Google Patents

Abstract

The invention provides a high-precision time service card applied to task navigation. A lithium battery module is used for supplying power to a temperature-compensation crystal oscillator module and a frequency control module; the temperature-compensation crystal oscillator module is used for outputting a calibrated frequency reference signal; the frequency control module is used for measuring the frequency precision of a temperature-compensation crystal oscillator, generating a corresponding frequency regulation voltage and outputting the frequency regulation voltage to the voltage control end of the temperature-compensation crystal oscillator; meanwhile the frequency control module is in charge of achieving a communication function with ground time service equipment and an onboard task navigation system. The high-precision time service card can be used for ensuring that when airborne equipment has no satellite signal or the satellite signals are disturbed, the task navigation system can still acquire time reference information which meets requirements from the time service card, so that the task reliability of a whole helicopter port electronic system is improved.

Description

A kind of high precision time service card that is applied to task navigation

Technical field

The present invention relates to a kind of high precision time service card.

Background technology

Aircraft platform, when carrying out aerial mission, need to be guaranteed by task navigational system consistance and the accuracy in aircraft platform time, space.The time service mode that task navigation subsystem adopts is at present after taking off, and obtains the temporal information of satellite from inertial navigation system, then by high-precision frequency reference source, guarantees the exactly operation of time.The shortcoming of which be if system start time satellite-signal be interfered, task navigation subsystem cannot be obtained initial time, also just cannot provide time reference information to other system on machine, will finally cause the inefficacy of task.Therefore how for task navigation subsystem provides a kind of time service means reliably, as the one backup of satellite time transfer, become urgent problem in practical application.

Summary of the invention

In order to overcome the deficiencies in the prior art, the invention provides a kind of high precision time service card, can pass through pps pulse per second signal and time message from ground time service equipment acquisition time information, and this information is passed to task navigational system on machine, guarantee when airborne equipment is interfered without satellite-signal or satellite-signal, task navigational system still can be obtained the time reference information meeting the demands from time service card, thereby has improved the mission reliability of whole aircraft platform electronic system.

The technical solution adopted for the present invention to solve the technical problems is: comprise lithium battery module, temperature compensating crystal oscillator module and frequency control module.

Described lithium battery module is temperature compensating crystal oscillator module and frequency control module power supply; Described temperature compensating crystal oscillator module output is through the frequency reference signal of calibration; Described frequency control module is measured the frequency accuracy of temperature compensating crystal oscillator, generate the frequency of answering in contrast and adjust voltage, and by this Voltage-output the voltage-controlled end to temperature compensating crystal oscillator, simultaneously frequency control module be responsible for ground time service equipment and machine on the communication function of task navigational system.

Described frequency control module comprises pulse per second (PPS) synchronization module, high precision time interval measurement module, one-chip computer module and D/A modular converter; Pulse per second (PPS) synchronization module generates the pps pulse per second signal of synchronizeing with ground time service equipment under the control of one-chip computer module, high precision time interval measurement module is measured the time interval of synchronous pulse per second (PPS) and ground time service equipment pulse per second (PPS), and one-chip computer module reads the time interval and according to formula calculate the frequency departure of temperature compensating crystal oscillator, wherein, Δ f is the side-play amount of temperature compensating crystal oscillator output frequency and nominal value, f _reffor the nominal value of temperature compensating crystal oscillator frequency output, f _xfor the actual frequency output of temperature compensating crystal oscillator, Δ t _i+1be the ground time service equipment pulse per second (PPS) that records second of i+1 and synchronize the interval of pulse per second (PPS), Δ t _ibe the ground time service equipment pulse per second (PPS) that records second of i and synchronize the interval of pulse per second (PPS), τ is reference time; One-chip computer module calculates corresponding frequency and adjusts controlled quentity controlled variable $\mathrm{adjust}=\frac{V_{\mathrm{range}}}{F_{\mathrm{range}}}\×\frac{\mathrm{\Δf}}{f_{\mathrm{ref}}}\×\frac{2^m-1}{V_{\mathrm{range}}}=\frac{\mathrm{\Δf}}{f_{\mathrm{ref}}}\×\frac{2^{m-1}}{F_{\mathrm{range}}},$ By D/A converter, frequency is adjusted to the voltage-controlled end of Voltage-output to temperature compensating crystal oscillator, wherein, V _rangerepresent to control input voltage range, F _rangerepresent frequency pulling scope, Δ f/f _refthe frequency departure amount that represents temperature compensating crystal oscillator, m represents the figure place of D/A converter; Described one-chip computer module is connected with pulse per second (PPS), the time service interface of task navigational system with ground time service equipment, and temporal information is passed on machine by ground.

The invention has the beneficial effects as follows: time service card of the present invention possesses frequency calibration function, when time service card inserts ground time service equipment, the pulse per second (PPS) that automatically utilizes time service equipment is carried out to frequency calibration to the temperature compensating crystal oscillator on time service card, original frequency accuracy is that temperature compensating crystal oscillator its frequency accuracy after calibration of 10-8 can reach 10-9, both promoted the punctual precision of time service card, also avoid the output frequency that causes because crystal oscillator is aging inaccurate simultaneously, guaranteed the performance index of time service card in life cycle.

The sequential of the Start signal of time service card of the present invention to high precision time interval measurement module, Stop1 signal, Stop2 signal has been carried out well-designed, the 2 road pps pulse per second signals of guaranteeing Stop1 signal, the representative of Stop2 signal arrive TDC device according to fixing order, in the time range of 2 μ s, thereby avoided measurement range to exceed the situation of device measurement capability, simplified design.

Time service card of the present invention is from ground time service equipment is extracted, and, in punctual state, its punctual precision can be better than 1ms/24h, and owing to having adopted low power dissipation design, its stand-by time can reach 1 week.

Time service card of the present invention erects the bridge of time transmission first between ground time service equipment and airborne equipment, becomes a need for reliable backup of task navigational system acquisition time reference information.

Accompanying drawing explanation

Fig. 1 is structural representation of the present invention.

Embodiment

Below in conjunction with drawings and Examples, the present invention is further described, the present invention includes but be not limited only to following embodiment.

Time service card comprises lithium battery module, temperature compensating crystal oscillator module, frequency control module composition.The exportable 3.3V voltage signal of lithium battery module, guarantees that time service card is in the normal operation of carrying each module in process, and this module, with charging inlet, can be its charging by ground time service equipment simultaneously.The output of temperature compensating crystal oscillator module is through the frequency reference signal of calibration, for steady, the accurate operation of time service card time is given security.Frequency control module can be measured the frequency accuracy of temperature compensating crystal oscillator, generate the frequency of answering in contrast and adjust voltage, and by this Voltage-output the voltage-controlled end to temperature compensating crystal oscillator.Simultaneously frequency control module be responsible for ground time service equipment and machine on the communication function of task navigational system.

Frequency control module comprises pulse per second (PPS) synchronization module, high precision time interval measurement module, one-chip computer module and D/A modular converter.Pulse per second (PPS) synchronization module can generate the pps pulse per second signal of synchronizeing with ground time service equipment under the control of single-chip microcomputer.High precision time interval measurement module can realize synchronous pulse per second (PPS) and the precision measurement in the ground time service equipment pulse per second (PPS) time interval.Single-chip microcomputer is by reading the measurement result in the two-way pulse per second (PPS) time interval, according to

formula calculate the frequency departure of temperature compensating crystal oscillator.Wherein Δ f is the side-play amount of temperature compensating crystal oscillator output frequency and nominal value, f _reffor the nominal value of temperature compensating crystal oscillator frequency output, f _xfor the actual frequency output of temperature compensating crystal oscillator, Δ t _i+1be the ground time service equipment pulse per second (PPS) that records second of i+1 and synchronize the interval of pulse per second (PPS), Δ t _ibe the ground time service equipment pulse per second (PPS) that records second of i and synchronize the interval of pulse per second (PPS), τ is reference time, at this, represents 1s.Single-chip microcomputer goes out corresponding frequency and adjusts controlled quentity controlled variable according to the frequency departure of temperature compensating crystal oscillator, control input voltage range, frequency pulling range computation, by D/A converter, frequency is adjusted to the voltage-controlled end of Voltage-output to temperature compensating crystal oscillator.The computing formula that frequency is adjusted controlled quentity controlled variable is as follows: $\mathrm{adjust}=\frac{V_{\mathrm{range}}}{F_{\mathrm{range}}}\×\frac{\mathrm{\Δf}}{f_{\mathrm{ref}}}\×\frac{2^m-1}{V_{\mathrm{range}}}=\frac{\mathrm{\Δf}}{f_{\mathrm{ref}}}\×\frac{2^{m-1}}{F_{\mathrm{range}}}.$ Wherein adjust represents frequency adjustment controlled quentity controlled variable, V _rangerepresent to control input voltage range, F _rangerepresent frequency pulling scope, Δ f/f _refthe frequency departure amount that represents temperature compensating crystal oscillator, m represents the figure place of D/A converter.

Single-chip microcomputer is connected with pulse per second (PPS), the time service interface of task navigational system with ground time service equipment respectively by I/O pin simultaneously, completes temporal information is passed to the task on machine by ground.

As shown in Figure 1, time service card of the present invention comprises the ingredients such as lithium battery module, temperature compensating crystal oscillator module, pulse per second (PPS) synchronization module, high precision time interval measurement module, one-chip computer module, D/A converter.

Consider the factors such as volume, weight and power consumption, lithium battery module is selected voltage 3.3V, and the lithium battery group that capacity is 7Ah is responsible for time service card and provides energy moving in process, guarantees the correct transmission of time.Time service card power consumption is pressed 500mW and is calculated, and its standby working time is 3.3V*7Ah/500mW, is about 2 days, can meet mission requirements.

Temperature compensating crystal oscillator selects short stability can reach 10 ^-10, frequency accuracy reaches 10 ^-8temperature compensating crystal oscillator, when time service card works in punctual state, its punctual precision 1*10 ^-8* 3600000ms/ hour, is about 36 μ s/h, and its punctual precision of the time of one day, within 1ms, can meet mission requirements.

Pulse per second (PPS) synchronization module is comprised of rising edge testing circuit, counter circuit, pulse per second (PPS) generative circuit, and foregoing circuit is all exported as clock signal using the frequency of temperature compensating crystal oscillator, generates the pps pulse per second signal of synchronizeing with input pulse per second (PPS).

High precision time interval measurement module is mainly comprised of several digital conversion chips (TDC) and peripheral circuit thereof.

Scheme 1: using the 1PPS(Pulse Per Second of ground time service equipment) signal is as the Start signal of TDC chip, the 1PPS signal of exporting using pulse per second (PPS) synchronization module, as Stop signal, is completed the accurate measurement at 2 signal rising time intervals automatically by TDC chip.The shortcoming of this scheme is that the rising edge of requirement Start signal and the rising edge interval of Stop signal are greater than 3.5ns, and Measurement Resolution is 65ps, and constraint condition is more.

Scheme 2: first send a dummy start signal that does not participate in measuring but will trigger measurement by single-chip microcomputer, notice TDC chip enters measuring state, using the 1PPS signal of ground time service equipment as Stop1 signal, using the 1PPS signal of pulse per second (PPS) synchronization module output as Stop2 signal, the measurement result of the measurement result of Stop1 signal and Stop2 signal is subtracted each other to the time interval that can obtain 2 road pps pulse per second signals.The advantage of this scheme is to have adopted dummy start signal, and this signal can accurately be controlled by single-chip microcomputer, to unconditionally constraint of 2 tested road PPS signals.In addition adopt the mode of this scheme employing difference measurement, can effectively reduce quantization error and the systematic error of systematic survey.

One-chip computer module is mainly comprised of low-power scm and peripheral circuit thereof, and process control and the result of being responsible for 2 road pps pulse per second signal time interval measurements read, according to

formula calculate the frequency departure of temperature compensating crystal oscillator.Wherein Δ f is the side-play amount of temperature compensating crystal oscillator output frequency and nominal value, f _reffor the nominal value of temperature compensating crystal oscillator frequency output, f _xfor the actual frequency output of temperature compensating crystal oscillator, Δ t _i+1be the ground time service equipment pulse per second (PPS) that records second of i+1 and synchronize the interval of pulse per second (PPS), Δ t _ibe the ground time service equipment pulse per second (PPS) that records second of i and synchronize the interval of pulse per second (PPS), τ is reference time, is decided to be herein 1s.Single-chip microcomputer continuous coverage 60 times, obtain 60 groups of measurement data, then utilize least square method to simulate the frequency departure amount of temperature compensating crystal oscillator, and according to the control input voltage range of temperature compensating crystal oscillator, frequency pulling range computation, go out corresponding frequency and adjust controlled quentity controlled variable, by D/A converter, frequency is adjusted to voltage adjustment and is exported to the voltage-controlled end of temperature compensating crystal oscillator.

The computing formula that frequency is adjusted controlled quentity controlled variable is as follows:

$\mathrm{adjust}=\frac{V_{\mathrm{range}}}{F_{\mathrm{range}}}\×\frac{\mathrm{\Δf}}{f_{\mathrm{ref}}}\×\frac{2^m-1}{V_{\mathrm{range}}}=\frac{\mathrm{\Δf}}{f_{\mathrm{ref}}}\×\frac{2^{m-1}}{F_{\mathrm{range}}}.$

Wherein adjust represents frequency adjustment controlled quentity controlled variable, V _rangerepresent to control input voltage range, F _rangerepresent frequency pulling scope, Δ f/f _refthe frequency departure amount that represents temperature compensating crystal oscillator, m represents the figure place of D/A converter.Single-chip microcomputer is connected with pulse per second (PPS), the time service interface of task navigational system with ground time service equipment respectively by I/O pin, and the mode combining with time message by pulse per second (PPS) completes temporal information is passed to the task on machine by ground

The digital control amount that D/A converter can send according to single-chip microcomputer generates the voltage signal of simulation, exports the voltage-controlled end of temperature compensating crystal oscillator to, and its frequency signal is revised.

Claims (2)

1. a high precision time service card that is applied to task navigation, comprises lithium battery module, temperature compensating crystal oscillator module and frequency control module, it is characterized in that: described lithium battery module is temperature compensating crystal oscillator module and frequency control module power supply; Described temperature compensating crystal oscillator module output is through the frequency reference signal of calibration; Described frequency control module is measured the frequency accuracy of temperature compensating crystal oscillator, generate the frequency of answering in contrast and adjust voltage, and by this Voltage-output the voltage-controlled end to temperature compensating crystal oscillator, simultaneously frequency control module be responsible for ground time service equipment and machine on the communication function of task navigational system.

2. the high precision time service card that is applied to task navigation according to claim 1, is characterized in that: described frequency control module comprises pulse per second (PPS) synchronization module, high precision time interval measurement module, one-chip computer module and D/A modular converter; Pulse per second (PPS) synchronization module generates the pps pulse per second signal of synchronizeing with ground time service equipment under the control of one-chip computer module, high precision time interval measurement module is measured the time interval of synchronous pulse per second (PPS) and ground time service equipment pulse per second (PPS), and one-chip computer module reads the time interval and according to formula

calculate the frequency departure of temperature compensating crystal oscillator, wherein, Δ f is the side-play amount of temperature compensating crystal oscillator output frequency and nominal value, f _reffor the nominal value of temperature compensating crystal oscillator frequency output, f _xfor the actual frequency output of temperature compensating crystal oscillator, Δ t _i+1be the ground time service equipment pulse per second (PPS) that records second of i+1 and synchronize the interval of pulse per second (PPS), Δ t _ibe the ground time service equipment pulse per second (PPS) that records second of i and synchronize the interval of pulse per second (PPS), τ is reference time; One-chip computer module calculates corresponding frequency and adjusts controlled quentity controlled variable $\mathrm{adjust}=\frac{V_{\mathrm{range}}}{F_{\mathrm{range}}}\×\frac{\mathrm{\Δf}}{f_{\mathrm{ref}}}\×\frac{2^m-1}{V_{\mathrm{range}}}=\frac{\mathrm{\Δf}}{f_{\mathrm{ref}}}\×\frac{2^{m-1}}{F_{\mathrm{range}}},$ By D/A converter, frequency is adjusted to the voltage-controlled end of Voltage-output to temperature compensating crystal oscillator, wherein, V _rangerepresent to control input voltage range, F _rangerepresent frequency pulling scope, Δ f/f _refthe frequency departure amount that represents temperature compensating crystal oscillator, m represents the figure place of D/A converter; Described one-chip computer module is connected with pulse per second (PPS), the time service interface of task navigational system with ground time service equipment, and temporal information is passed on machine by ground.

Images